CN111788271B - Ink for ink-jet printer with electrification control - Google Patents

Abstract

An object of the present invention is to provide ink for an ink jet printer that can reduce the addition rate of a conductive agent and has a low resistance. In order to solve the above-mentioned technical problems, the charge control ink for inkjet printers according to the present invention is characterized in that it contains resin, pigment, conductive agent and non-aqueous solvent, and the conductive agent is a salt that generates anions and cations in the non-aqueous solvent Structure, the anion has a trifluoromethanesulfonyl group, and the cation is a quaternary ammonium cation or has an unsaturated heterocyclic structure.

Description

Ink for inkjet printer with charging control method

technical field

The present invention relates to an ink for an ink jet printer of a charging control method.

Background technique

Inkjet printers with a charge control method are used in a wide range of fields, such as food and electronic products, to print expiration dates, expiration dates, and manufacturing numbers. The ink of the charge-controlled inkjet printer is mainly composed of resin, colorant, conductive agent, and solvent. Additives such as a leveling agent for controlling the shape of printed dots are added thereto.

Colorants are added for color development of the ink. Resin is added in order to hold materials such as colorants in the printed part. As the leveling agent, a silicone-based compound is usually used.

In an ink jet printer of a charging control method, ink particles ejected from a nozzle are charged, and are deflected by a deflection electrode to eject ink on a printing surface. Therefore, it is necessary to charge the ink. In order to impart a suitable charge to the ink droplets, a conductive agent is added. Specifically, the conductive agent has the function of increasing the conductivity of the ink and reducing the resistance.

As the conductive agent, an organic substance having a salt structure is generally used.

Patent Document 1 discloses an inkjet ink composition containing an organic solvent such as acetone and propylene glycol methyl ether, a solvent-soluble binder resin, and a water-insoluble quinone dye. In addition, as a conductive agent, it is disclosed that lithium trifluoromethanesulfonate can be used.

In Patent Document 2, as a conductive ink for preparing an organic photovoltaic cell, a compound containing an organic semiconductor, an organic solvent, and an additive for increasing conductivity is disclosed. As the conductive additive, it is disclosed that an alkali metal salt or an organic salt of which an anion is formed of trifluoromethanesulfonate (Triflate, Trifluoromethanesulfonate) or bis(trifluoromethanesulfonyl)imide can be used.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Publication No. 2010-503741

Patent Document 2: Japanese Patent Publication No. 2011-504650

SUMMARY OF THE INVENTION

The technical problem to be solved by the invention

The rubbing resistance and adhesion of the ink for inkjet printers are mainly borne by the resin, and can be added to an allowable viscosity for printing. When the ratio of the colorant or the conductive agent in the ink is increased, the ratio of the resin added to ensure the physical strength of the print decreases, so the abrasion resistance and the adhesiveness decrease. In order to ensure legibility, it is necessary to add a colorant. Therefore, it is difficult to reduce the content rate of the colorant. Therefore, it is desirable to maintain low resistance and reduce the addition rate of the conductive agent.

Since the conductive agent disclosed in Patent Document 1 is an inorganic substance such as an alkali metal, the cation has a technical problem in terms of solubility in resins and solvents.

The conductive compound disclosed in Patent Document 2 does not contain resins and colorants contained in inks for inkjet printers for the purpose of forming circuits and the like. Therefore, there is no technical problem that high adhesion and high abrasion resistance are required to be obtained by adding a resin, and a low resistance is required to be obtained by adding a conductive agent.

Therefore, the objective of this invention is to provide the ink for inkjet printers which can reduce the addition rate of a conductive agent and has low resistance.

Technical solutions for solving technical problems

In order to solve the above-mentioned technical problems, the charge control ink for inkjet printers according to the present invention is characterized in that it contains resin, pigment, conductive agent and non-aqueous solvent, and the conductive agent is a salt that generates anions and cations in the non-aqueous solvent Structure, the anion has a trifluoromethanesulfonyl group, and the cation is a quaternary ammonium cation or has an unsaturated heterocyclic structure.

Invention effect

According to the present invention, it is possible to provide ink for an ink jet printer that can reduce the addition rate of the conductive agent and has a low resistance.

Description of drawings

FIG. 1 is a schematic diagram showing a printing process of an ink jet printer of a charging control method.

FIG. 2 is a graph showing the electrical resistance of inks of Examples and Comparative Examples.

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like.

1. Ink for inkjet printers

The ink contains resin, colorant, non-aqueous solvent and conductive agent. These are stirred with a stirring blade, an overhead stirrer, or the like to dissolve each other, thereby forming ink.

＜Resin＞

The type of resin contained in the ink is not particularly limited as long as it can be dissolved in a solvent, and is selected in consideration of adhesion to a printing object (printing object), abrasion resistance, and the like. As resins, acrylic resins, styrene acrylic resins, polyvinyl butyral resins, polyester resins, chlorine-containing vinyl acetate, and mixtures of these resins can be specifically used. The weight average molecular weight of these resins is preferably about several thousand to 20,000. The content rate of the resin in the ink is preferably 5 mass % or more from the viewpoint of securing the rub resistance and adhesiveness of printing. In order to obtain a viscosity that enables printing, the content of the resin in the ink is preferably 15 mass% or less.

＜Colorant＞

As the colorant, dyes or pigments can be used.

(dye)

The dye is not particularly limited as long as it can be dissolved in the solvent used. Specifically, the following dyes can be mentioned. Examples of black-based dyes include Oil Black HBB (C.I. Solvent Black 3), VALIFASTBLACK 3804 (C.I. Solvent Black 34), SPIRITBLACKSB (C.I. Solvent Black 5), OLEOSOLFASTBLACKRL (C.I. Solvent Black 27), AIZENSOTBLACK8 (C.I. Solvent Black 7), ORASOLBLACKCN (C.I. Solvent Black 28) etc.

Examples of red-based dyes include Oil Red 5B (C.I. Solvent Red 27), VALIFASTRED 1306 (C.I. Solvent Red 109), OLEOSOLFASTREDBL (C.I. Solvent Red 132), AIZENSOTRED1 (C.I. Solvent Red 24), ORASOLRED3GL (C.I. Solvent Red 130), FILAMIDREDGR (C.I. Solvent Red 225) etc.

Examples of yellow dyes include Oil Yellow 129 (C.I. Solvent Yellow 29), OLEOSOLBRILLIANTYELLOW 5G (C.I. Solvent Yellow 150), AIZENSOTYELLOW 1 (C.I. Solvent Yellow 56), ORASOLYELLOW 3R (C.I. Solvent Yellow 25), and the like.

Examples of blue-based dyes include Oil Blue 2N (C.I. Solvent Blue 35), VALIFASTBLUE 1605 (C.I. Solvent Blue 38), OLEOSOLFASTBLUEELN (C.I. Solvent Blue 70), AIZENSOTBLUE1 (C.I. Solvent Blue 25), ORASOLBLUEGN (C.I. Solvent Blue 67), and the like .

(pigment)

As the pigment, when it is black, carbon black can be used. When white, titanium dioxide, zinc oxide, or the like can be used. In the case of red, cadmium red, iron oxide red (iron trioxide), quinacridone red, etc. can be used. In the case of yellow, chrome yellow, cadmium yellow, nickel titanium yellow, etc. can be used. In the case of blue, Prussian blue, copper phthalocyanine, or the like can be used. For green, phthalocyanine green, a mixture of chrome yellow and cyanine, titanium cobalt green, and the like can be used.

In addition to white pigments, the pigments are preferably pulverized to an average particle size of 100 nm to 1000 nm, and then used together with an appropriate dispersant. When the white pigment is too small, the masking ratio decreases, so the average particle diameter is preferably 200 nm or more, and it is added to the ink together with the dispersant.

<Non-aqueous solvent>

The non-aqueous solvent is not particularly limited as long as it can dissolve the resin and reduce the viscosity of the ink to allow printing. For example, organic solvents such as aromatic-based, ester-based, ketone-based, hydrocarbon-based, alcohol-based, and glycol-based solvents can be used. Among them, in the ink jet printer of the charging control method, the viscosity of the ink is controlled to about 1 to 5 mPa·S at 20°C. This is because the ink is not easily ejected from the print head when the viscosity is high.

As a solvent for the ink of an ink jet printer of a charging control method, ketone-based solvents such as 2-butanone (common name methyl ethyl ketone (MEK)), acetone, and methyl isopropyl ketone are generally used. In addition to easily dissolving the resin, these solvents have a high vapor pressure, so they dry quickly after printing. Therefore, it is preferable that the resin and the conductive agent have high solubility in the ketone-based solvent. In addition to the ketone-based solvent, dimethoxyethane and ethanol can be used as the solvent.

＜Conductive agent＞

The conductive agent has a salt structure that generates an anion and a cation in a non-aqueous solvent, the anion has a trifluoromethanesulfonyl group (CF ₃ SO ₂ ), and the cation is a quaternary ammonium cation or has an unsaturated heterocyclic structure.

(anion)

When the content ratio of the conductive agent in the ink is increased, the content ratio of the resin added in order to ensure the physical strength of printing in the ink (in the printing) decreases, so that the rubbing resistance and adhesion of the printing decrease. Therefore, it is necessary to reduce the addition rate of the conductive agent as much as possible.

From the research results of the present inventors, it was found that in the salt structure constituting the conductive agent, the acid to which a proton is bonded as an anion is more acidic, and the addition amount thereof is small and the conductivity is high. One of the parameters indicating the strength of acid is Hammett's acidity function, and it has been found that the acidity function is preferably -12 or less.

In addition, it is also necessary that the substances in the ink composition hardly undergo oxidation and reduction reactions. Furthermore, unlike strong acids such as perchloric acid and nitric acid, it is also required that it does not exhibit oxidizing properties against substances in the ink composition. It is also required to be chemically stable even if it becomes an anion, and to exhibit little reducibility and nucleophilicity. That is, a strongly acidic and chemically stable acid is desired. As an anion corresponding to this, the _anion which has a trifluoromethanesulfonyl group (CF3SO2 ₎ is mentioned. Specifically, trifluoromethanesulfonate (conjugate base of trifluoromethanesulfonic acid) represented by CF ₃ SO ₃ ^— and bis(trifluoromethanesulfonyl)imide represented by (CF ₃ SO ₂ ) ₂ N ^— The conjugate base of , the conjugate base of tris(trifluoromethanesulfonyl) methide represented by (CF ₃ SO ₂ ) ₃ C ^- , etc.

(cation)

As the conductive agent, it is necessary to use a substance that can be dissolved in a non-aqueous solvent. With regard to inks, ketone-based solvents such as MEK are the mainstream, and therefore, the conductive agent is preferably a substance dissolved in a ketone-based solvent such as MEK. In order to improve the solubility to a solvent, in the present invention, an organic substance is used instead of an inorganic substance such as an alkali metal such as Li and Na as a cation. Specifically, the cation is a quaternary ammonium cation having 1 to 4 alkyl chains (a cation having a quaternary ammonium salt structure), or a cation having an unsaturated heterocyclic ring.

As a cation which has a quaternary ammonium salt structure, the amine which has an alkyl chain of a linear structure or a branched structure, and the amine which has a heterocyclic structure, such as pyrrole and pyridine, are mentioned.

In addition, the unsaturated heterocyclic structure preferably contains nitrogen, and is more preferably a monocyclic unsaturated six-membered ring structure or a monocyclic unsaturated five-membered ring structure.

In order to reduce the addition rate to the ink, the molecular weight of the cation is preferably small. Tetraalkylammonium salts (cations are tetraalkylammonium ions) commonly used as conductive agents for inks, the longer the alkyl group, the higher the solubility in organic solvents. Therefore, it is preferable to use, as a cation, a tetraalkylammonium ion having an alkyl group having 4 or more carbon atoms in an ink jet printer ink of a charge control system. However, when a tetraalkylammonium ion having an alkyl group having 4 or more carbon atoms is used as a cation, the molecular weight is large. When calculating the molecular weight of an element by rounding off the decimal point, when the number of carbon atoms in the alkyl group is 4, the molecular weight is 308; when the number of carbon atoms is 6, the molecular weight is 420; when the number of carbon atoms is 8, the molecular weight is 532; in the case of tetraphenylamine, the molecular weight is also 392; in order to improve the solubility in organic solvents, the molecular weight is also 464 in the case of a phenyl group into which a fluorine group is introduced.

On the other hand, by making the cation into a monocyclic unsaturated heterocyclic ring, the molecular weight can be reduced. For example, when the molecule does not have an alkyl group, the molecular weights of the imidazolium structure and the pyrrolium structure having a monocyclic unsaturated five-membered ring structure are as small as 69 and 72, respectively. Moreover, when it does not have an alkyl group in a molecule|numerator, the molecular weight of the pyridinium structure which has a monocyclic unsaturated six-membered ring structure is as small as 80. In these structures, solubility in organic solvents can be ensured by introducing one or two alkyl groups into nitrogen in the molecule. However, when the alkyl group is too long, the solubility in alcohol-based solvents such as ethanol also decreases. Therefore, when the unsaturated heterocyclic structure is a pyridinium structure, it is preferable that the total number of carbon atoms of the hydrocarbon groups of the straight-chain structure or branched structure bonded to the nitrogen of the pyridinium structure is 4-10. In addition, when the unsaturated heterocyclic structure is an imidazolium structure, the total number of carbon atoms of the straight-chain structure or branched structure hydrocarbon groups bonded to the nitrogen of the imidazolium structure is preferably 2 to 8. In addition, when the unsaturated heterocyclic structure is a pyrrolium structure, the total number of carbon atoms of the hydrocarbon groups of the linear structure or branched structure bonded to the nitrogen of the pyrrolium structure is preferably 4 to 8.

By using the above-mentioned cations, the solubility in non-aqueous solvents commonly used in inks for ink jet printers is improved.

In addition, by making the cation into a nitrogen-containing unsaturated heteromonocycle, a conductive agent having a trifluoromethanesulfonyl acid salt structure with a small molecular weight can be obtained.

Next, the introduction site of the alkyl group will be described. Since the nitrogen at the 1-position is quaternized, the hydrophilicity is high. In other words, since the hydrophobicity is low, it is preferable to introduce a hydrophobic alkyl group into the nitrogen at the 1-position in order to improve the solubility of the nitrogen site in a hydrophobic organic solvent such as MEK.

In addition, as the introduction site of the alkyl group other than the 1-position, a site distant from nitrogen is preferable. The 3rd or 4th position is preferable to the 2nd position. This is due to the easy approach of anions to the vicinity of nitrogen, thereby improving the thermal stability of the salt structure. When an alkyl group is present at the 2-position, steric hindrance occurs and the approach of an anion to nitrogen is prevented, so that the thermal stability of the salt tends to decrease. It is important to ensure thermal stability because the ink may be heated to several tens of degrees in the vicinity of a heat-generating part such as a pump inside an inkjet printer. Therefore, in order to secure thermal stability, the introduction site of the alkyl group other than the 1-position is also preferably a site distant from nitrogen, such as the 3-position and the 4-position.

According to the above description, when the unsaturated heterocyclic structure is a pyridinium structure, as shown in Chemical formula 1, a hydrocarbon group with a linear or branched structure is preferably bonded to the 1- and 3-positions of the pyridinium structure. The total number of carbon atoms of the position-bonded hydrocarbon groups is 4 to 10.

In Chemical Formula 1, R1 and R2 are each an independent alkyl group, and the total number of carbon atoms of R1 and R2 is 4 or more and 10 or less. In addition, when the unsaturated heterocyclic structure is an imidazolium structure, as shown in Chemical formula 2, it is preferable that the 1-position and the 3-position of the imidazolium structure have a straight-chain structure or a branched hydrocarbon group bonded thereto, and preferably the 1-position and the 3-position bond. The total number of carbon atoms of the combined hydrocarbon group is 2 to 8.

In Chemical Formula 2, R1 and R2 are each an independent alkyl group, and the total number of carbon atoms of R1 and R2 is 2 or more and 8 or less.

In addition, when the unsaturated heterocyclic structure is a pyrrolium structure, a hydrocarbon group having two linear or branched structures bonded to the 1-position of the pyrrolium structure represented by Chemical Formula 3 is preferable, and two hydrocarbon groups bonded to the 1-position are preferable. The total number of carbon atoms is 4-8.

In Chemical Formula 3, R1 and R2 are each an independent alkyl group, and the total number of carbon atoms of R1 and R2 is 4 or more and 8 or less.

Therefore, as the conductive agent, compounds represented by compound group 1, compound group 2, and compound group 3 described below are preferable.

In compound group 1, R1 and R2 are each an independent alkyl group, and the total number of carbon atoms of R1 and R2 is 2 or more and 8 or less. n is an integer of 1 or more and 3 or less, when n is 1, X is oxygen, when n is 2, X is nitrogen, and when n is 3, X is carbon.

In compound group 2, R1 and R2 are each independent alkyl groups, and the total number of carbon atoms of R1 and R2 is 4 or more and 8 or less. When n is 1 or more and 3 or less, when n is 1, X is oxygen, when n is 2, X is nitrogen, and when n is 3, X is carbon.

In compound group 3, R1 and R2 are each an independent alkyl group, and the total number of carbon atoms of R1 and R2 is 4 or more and 10 or less. When n is 1 or more and 3 or less, when n is 1, X is oxygen, when n is 2, X is nitrogen, and when n is 3, X is carbon.

When comparing the molecular weights of compound group 1, compound group 2 and compound group 3, the molecular weight of compound group 1 is 97-181, the molecular weight of compound group 2 is 180-292, and the molecular weight of compound group 3 is 136-220. Therefore, the compound group 1 is particularly preferably used as a conductive agent from the viewpoint of solubility in a solvent.

As the ink for an inkjet printer, a photocurable ink that is cured by irradiation with light such as ultraviolet rays can be used. Photocurable inks contain solvents, resins, colorants, conductive agents, resin precursors, polymerization initiators, and the like. As the solvent, resin, colorant, and conductive agent, the same compounds as the above-mentioned inks can be used.

The resin precursor has double bonds that can be polymerized. By irradiating the resin precursor with light such as ultraviolet rays in the presence of a polymerization initiator, a polymer is formed and cured.

As a resin precursor, an acrylic monomer or a methacrylate monomer can be mentioned. Examples of acrylic monomers include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, stearyl acrylate, isopropyl acrylate, Isobutyl acrylate, 2-ethylbutyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, cyclooctyl acrylate, cyclodecyl acrylate, methoxy polyethylene glycol acrylate, phenoxy Polyethylene glycol acrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, 1,8-octanediol diacrylate , 10-decanediol, diacrylate-1,12-dodecanediol, trimethylolpropane triacrylate, etc. As the methacrylate monomer, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, and decyl methacrylate can be used. , Dodecyl methacrylate, Stearyl methacrylate, Isopropyl methacrylate, Isobutyl methacrylate, 2-ethylbutyl methacrylate, 2-ethylhexyl methacrylate ester, cyclohexyl methacrylate, cyclooctyl methacrylate, cyclodecyl methacrylate, methoxypolyethylene glycol methacrylate, phenoxyethylene glycol methacrylate, dimethacrylic acid Ethylene glycol ester, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol 1,8-octanediol methacrylate, 1,10-decanediol dimethacrylate, glycerol dimethacrylate, polypropylene dimethacrylate, and the like.

The polymerization initiator is selected according to the type of polymerization reaction. The structure of the initiator includes peroxide-based, alkyl phenone-based, oxime ester-based and the like. As the peroxide, for example, azobisisobutyronitrile, benzoyl peroxide, and di-tert-butyl peroxide can be used; as the alkyl phenone series, 2,2-dimethoxy-1,2 can be used - Diphenylpropan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide; As the oxime ester system, 1,2-octanedione, 1-[4-(phenylthio)-2-(o-benzoyloxime)], etc. can be used.

2. Inkjet printer

The ink described above can be put into an ink jet printer to perform printing, and a desired printing can be provided.

FIG. 1 shows the printing process from the discharge of the ink of the charging control type ink jet printer to the liquid application. The ink droplet 2 ejected from the nozzle 1 is charged by the charging electrode 3 , and thereafter, the direction is controlled by the deflection electrode 4 , and then the ink droplet lands on the substrate 5 to be printed. Unprinted ink is recovered by the recovery tank 6 and returned to the ink cartridge (not shown in FIG. 1 ).

The dot size of the printed ink is about 300 to 400 μm. When the substrate to be printed is a resin surface such as polypropylene (PP) and polyethylene (PE), the dot size is as small as about 300-350 μm due to the high hydrophobicity of the substrate to be printed. On the other hand, when printing is performed on the surface of a highly hydrophilic aluminum can or glass bottle, the dot size is about 350 to 400 μm.

Example

Hereinafter, the Example of this invention is illustrated.

<Preparation of Inks 1 to 26>

Titanium dioxide powder (100 g) having an average particle diameter of 300 nm, polyvinyl butyral resin (32 g) having a hydroxyl value of 130 and a weight average molecular weight of 15,000, and 2-butanone (308 g) were mixed with a bead mill to prepare a titanium dioxide powder. Dispersions. To this were added an acrylic resin (100 g) having an acid value of 74 and a weight average molecular weight of 10,000, a polydimethylsiloxane derivative (2 g) having polyethoxy chains at both ends represented by the following chemical formula 4, and Conductive agent.

As the conductive agent, compounds 1-17 shown below were used, and the addition amount was 3 g or 5 g.

When the addition amount of the conductive agent was 3 g, 455 g of 2-butanone was added thereto; when the addition amount of the conductive agent was 5 g, 453 g of 2-butanone was added thereto. Then, except for the titanium dioxide, the mixture was stirred until dissolved, and 1 kg of each of the inks 1 to 26 was prepared. The composition of the prepared ink is shown in Table 1. Among them, when the addition amount of the conductive agent is 3g, the addition rate of the conductive agent in the ink is 0.3% by mass; when the addition amount of the conductive agent is 5g, the addition rate of the conductive agent in the ink is 0.5% by mass.

[Table 1]

<Preparation of inks 27 to 29>

Except using polyester with weight average molecular weight of 3000 (dicarboxylic acid unit is isophthalic acid:terephthalic acid = 1:1, diol unit is propylene glycol) instead of acrylic resin with acid value of 72 and weight average molecular weight of 10000 Except for (100 g), inks 27, 28, and 29 were prepared in the same manner as inks 1, 3, and 5, respectively.

<Preparation of Inks 30 to 32>

Inks 30, 31, and 32 were prepared in the same manner as inks 1, 3, and 5, except that carbon black powder (50 g) and MEK (50 g) having an average particle diameter of 150 nm were used instead of titanium dioxide powder (100 g) having an average particle diameter of 300 nm.

<Preparation of Ink 33>

A polyvinyl butyral resin (30 g) and MEK (570 g) having a hydroxyl value of 130 and a weight average molecular weight of 15,000 were mixed with carbon black powder (50 g) having an average particle size of 150 nm using a bead mill to prepare dispersion of carbon black. liquid. Thereto were added 1,6-hexanediol diacrylate (100 g) and dipropylene glycol diacrylate (100 g) as resin precursors, and 2,4,6-trimethylbenzoyl diacrylate as a polymerization initiator Phenylphosphine oxide (50 g), compound 5 (100 g) as a conductive agent, and stirred well. Thereby, the UV curable ink 33 is prepared.

<Resistance measurement of ink>

About the prepared ink 1-33, the electrical resistance of the ink was measured using the electrical conductivity meter ES-51 by Horiba Corporation. The measurement results are shown in Table 1 and FIG. 2 .

According to Table 1 and FIG. 2 , in inks 1-16 and 27-33, the resistance values of the inks were all 2000 Ω·cm or less when the addition ratio of the conductive agent was 0.3 mass % or 0.5 mass %.

From the results of Ink 1-16, it can be seen that by combining any anion of CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , and (CF ₃ SO ₂ )3C ^- with an anion having an imidazolium structure, a pyrrolium structure or The salt of the cation of the pyridinium structure is used as a conductive agent, and even if the addition rate is as small as 0.3 mass %, the resistance can be reduced to 2000 Ω·cm or less.

This is considered to be because the anions of the compounds 1 to 8 used as the conductive agent contain the conjugate base of trifluoromethanesulfonic acid as a super acid, and the dissociation degree as a salt is large.

From the results of Inks 27 to 29, it can be seen that even if the type of resin is changed, by combining any anion among CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , and (CF ₃ SO ₂ ) ₃ C ^- with imidazolium A salt of a cation with a structure, a pyrrolidinium structure or a pyridinium structure is used as a conductive agent, and can also greatly reduce the resistance of the ink at a small addition rate.

From the results of Inks 30 to 32, it can be seen that even if the type of pigment is changed, by combining any anion among CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , and (CF ₃ SO ₂ ) ₃ C ^- with imidazolium A salt of a cation with a structure, a pyrrolidinium structure or a pyridinium structure is used as a conductive agent, and can also greatly reduce the resistance of the ink at a small addition rate.

On the other hand, regarding the inks 17, 19, 21, and 23-26, the resistance values of the inks exceeded 2000 Ω·cm. Regarding the inks 18, 19, and 22, the electrical resistance was 2000 Ω·cm or less, but the addition rate of the conductive agent was as high as 0.5% by mass.

Regarding the inks 17 to 26, it is considered that the resistance of the inks increased because the anions constituting the conductive agent were bromide ions. From the above results, it has been found that in the chemical structure of the conductive agent, the anion has a structure containing CF ₃ SO ₂ , whereby the ink resistance can be greatly reduced and good printing can be performed.

＜Ink Printing Evaluation＞

The prepared inks 1 to 33 were filled in an ink jet printer UX model manufactured by Hitachi Sanki Systems Co., Ltd., and the printing operation was confirmed. The printing results are shown in Table 1. In Table 1, "⊚" was used for good printing, "◯" when normal printing was possible, and "x" when printing was impossible.

Regarding the inks 1-16 and 27-33 as examples, it was confirmed that the printing was normal, and the printing was not disturbed, and it was confirmed that the printing was good.

The inks 18 , 20 , 22 , and 26 with an addition rate of the conductive agent of 5% by mass were able to print normally, but the ink 24 could not be printed due to poor electrification. In addition, the inks 17, 19, 21, 23, and 25 in which the addition rate of the conductive agent was 3% by mass were all poorly charged, so that printing was not possible. The resistance of the inks that cannot be printed is 2100 Ω·cm or more. Therefore, it can be estimated that in order to be able to print, the resistance of the ink used needs to be less than 2100 Ω·cm.

From the above results, it was found that by combining any anion among CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , and (CF ₃ SO ₂ ) ₃ C ^- with an imidazolium structure, a pyrrolium structure or a pyridinium structure The salt of the cation of the conductive agent is used as a conductive agent, and good printing can be performed even if the addition rate of the conductive agent is small.

In addition, regarding the ink 33, after printing, it was confirmed that the printing was cured by irradiating the printing with light of 2 J/cm ² using an ultraviolet LED lamp capable of irradiating ultraviolet light of 365 nm. Therefore, even if a resin precursor is used instead of the resin, it has been found that the resistance of the ink can be greatly reduced with a small addition rate of the conductive agent having an anion having a trifluoromethanesulfonic acid structure, and good printing can be performed.

From the above results, it was found that the conductivity of the ink can be improved with a small addition amount by using a conductive agent composed of an ion having a trifluoromethanesulfonyl group and a cation having a quaternary ammonium cation or an unsaturated heterocyclic structure. With this ink, the effects of resin addition, such as adhesion and abrasion resistance, can be maintained, and the conductivity of the ink can be improved.

Symbol Description

1... nozzle, 2... ink droplet, 3... charged electrode, 4... deflection electrode, 5... printed substrate, 6... recovery tank.

Claims (4)

1. An ink for an ink-jet printer of a charge control system, characterized in that:

which comprises a resin, a pigment, a conductive agent and a nonaqueous solvent,

the conductive agent is a salt structure that generates anions and cations in the non-aqueous solvent,

the anion has a trifluoromethanesulfonyl group,

the cation has an unsaturated heterocyclic structure,

the unsaturated heterocyclic structure is a pyridinium structure or a pyrrolium structure,

a linear or branched hydrocarbon group bonded to the 1-and 3-positions of the pyridinium structure, wherein the total number of carbon atoms of the hydrocarbon groups bonded to the 1-and 3-positions of the pyridinium structure is 4 to 10,

2 hydrocarbon groups having a linear structure or a branched structure are bonded to the 1-position of the pyrrolium structure, and the total carbon number of the 2 hydrocarbon groups bonded to the 1-position of the pyrrolium structure is 4 to 8.

2. The ink for an ink jet printer of a charging control system according to claim 1, wherein:

the anion is CF ₃ SO ₃ ^－ 、(CF ₃ SO ₂ ) ₂ N ^－ 、(CF ₃ SO ₂ ) ₃ C ^－ Any of the above.

3. The ink for an ink jet printer of a charging control system according to claim 1 or 2, wherein:

further comprising a resin precursor and a polymerization initiator,

the resin precursor has a double bond capable of polymerization,

the ink is an ink that is cured by irradiation with ultraviolet rays.

4. The ink for an ink jet printer of a charging control system according to claim 1 or 2, wherein:

the acidity function of the anion is-12 or less.

Images